数据结构练习（18）左旋转字符串

http://zhedahht.blog.163.com/blog/static/2541117420073993725873/

#include <iostream>
#include <cstring>
using namespace std;

void reverse_string(char *s, char *e)
{
    if (s != nullptr && e != nullptr)
    {
        while (s < e)
        {
            char c = *e;
            *e = *s;
            *s = c;
            ++s, --e;
        }
    }
}

char* left_rotate_string(char *s, size_t n)
{
    if (s != nullptr)
    {
        size_t len = static_cast<int>(strlen(s)); 
        if (n > 0 && len > 0 && n < len)
        {
            reverse_string(s, s + n - 1);
            reverse_string(s + n, s + len - 1);
            reverse_string(s, s + len - 1);
        }
    }
    return s;
}

int main()
{
    char b[200];
    cin >> b;
    left_rotate_string(b, 2);
    cout << b;
    return 0;
}